DESCRIPTION: (applicant's abstract) The continued development, study, and bioanalytical applications of novel ion and polyion sensitive polymer membrane based electrochemical sensors are proposed. Research during the next project period will build upon recent discoveries regarding the favorable extraction thermodynamics of polyions (e.g., heparin, protamine, synthetic polypeptides) into plasticized polymeric films containing appropriate lipophilic ion-exchangers as well as selective interactions of anions with given metal ion-ligand complexes to devise sensors that will enable the direct detection of biomedically important species in complex samples, including whole blood. These efforts will include both fundamental and applied studies, with particular emphasis on expanding the range of species that can be monitored via simple phase boundary potentiometric (EMF) measurements across polymeric film/solution interfaces. Specific goals for the polyion sensor efforts include: a) using synthetic polycationic/polyanionic peptides as test compounds to determine how the polyion structure/charge density affects the thermodynamics of polyion extraction into appropriately formulated films; b) designing highly specific assays for protease enzymes using optimized synthetic polyion peptides as substrates; and c) investigating the ability to prepare simplified solid-state type polyion sensors using lipophilic silver ion/calixarene complexes as additional film additives. Beyond further studies of polyion sensing films, research on the use of metalloporphyrins as membrane active components in the development of new anion selective sensors will continue, specifically focusing on understanding the super-Nernstian behavior often observed with such systems, and on achieving analytically useful anion selectivities via changes in the metal center ion and addition of suitable lipophilic anion or cationic sites within the polymeric sensing films. Ongoing efforts to use the principles of molecular/ion imprinting to create more selective ion/polyion sensors will be accelerated by employing new photopolymerizable decyl methacrylate films, developed and studied in detail during the most recent grant period. It is anticipated that this research program will continue to provide the biomedical community with a wide array of new and/or improved chemical sensors as well novel sensor-based methods that will have immediate applications as tools for basic research and within modern clinical chemistry instrumentation.